Friday, December 30, 2011

Preaching To The Choir - On Why Plus/Minus Is Stupid, Part 38

Plus/Minus is often maligned by fancy stats types as not descriptive - it doesn't take into account the quality of competition or teammates. It doesn't acknowledge whether your team's goaltending is great, horrible, or somewhere in between. There's yet another reason why it's dumb - it describes game states that are not entirely relevant.

Let's take as an example my favorite team, the New Jersey Devils. They are having quite a bizarre season so far - 8-1 in shootouts, their record in regulation is a mere 10-15, but right now they're holding on to a playoff spot. More strange is their special teams play - they've scored a mere 17 power play goals, while allowing a whopping total of 11 short handed goals. Yet while shorthanded, they've only allowed 10 goals and have scored 7 short handed goals themselves. In addition, they've allowed 4 empty net goals and have scored none at even strength. All this has made the team plus minus even more useless than it already is, since as we know, plus/minus includes short handed and empty net goals.

Let's just look at the top 9 forwards' plus minus:

Forward

+/-

Adam Henrique

7

Petr Sykora

2

Dainius Zubrus

Even

Patrik Elias

-4

Zach Parise

-5

David Clarkson

-10

Ryan Carter

-11

Ilya Kovalchuk

-12

Mattias Tedenby

-14

Looks pretty bad, right? But when we take out short handed goals for and against as well as empty net goals, it looks a lot different:

Forward

+/-

+/- at ES

Difference

Adam Henrique

7

7

0

Petr Sykora

2

9

-7

Dainius Zubrus

Even

8

-8

Patrik Elias

-4

6

-10

Zach Parise

-5

2

-7

David Clarkson

-10

-4

-6

Ryan Carter

-11

-10

-1

Ilya Kovalchuk

-12

-1

-11

Mattias Tedenby

-14

-12

-2

We see a lot of pluses where there were minuses before. If we were using +/- to talk about even strength play on the Devils, most players have a radically different even strength +/-. We might erroneously think that Ilya Kovalchuk is having a horrible season at even strength, but he's merely been average-ish. What are we even looking to describe when we talk about +/-?